Help with Rough Engine Idle Triage (1 Viewer)

[jltemlock]

Hey Team:

My '93 FZJ80 randomly started having a consistent rough idle when in Gear (including Reverse). I'm interested in thoughts on what else I should investigate.

In park, I idle a little above 1K RPM and the engine runs smoothly. When I put her into gear, I kick down to about 700 RPM and experience a pretty significant rumble throughout the vehicle. When I take my foot off the brake (in forward or reverse) I get a choppy roll until I touch the gas. Once on the gas she runs smoothly until I get to my next stop when the rough idle and chop re-emerges.

Thus far I've checked the Idle Air Control Valve (getting the appropriate resistance readings), adjusted my TPS, and replaced a few of vacuum hoses that were starting to crack. If helpful, I also recently replaced the torque converter and trans oil pump, but I doubt those are related

Any other ideas on what I should investigate are much appreciated.

 

[inkpot]

Do a compression check.

 

[jltemlock]

Thanks, Inkpot. I've never done a compression check so sorry for the newb question. If a cylinder was losing pressure, would I feel the roughness throughout the ride vs just when in idle? Probably an obvious answer, but again- I'm a newb

Thanks in advance

 

[inkpot]

We have a local 93 that has been driven to the high country frequently over the last 4-5 years. We have made a couple of efforts to resolve a ruff idle, but we never resolved it. Recently dug a little deeper and found 2 cylinders with around 50-60 #. Compression leaking out via intake, so likely it is bad intake valves. Head gasket and head machine work to be done soon. Last valve job we did required only valve seals and gaskets to complete.